The present invention relates to a semiconductor device, and more specifically to a semiconductor device having increased immunity against .alpha.-particles and external noise.
In a conventional semiconductor device as disclosed, for example, in Japanese Patent Laid-Open No. 1556/1981, a p-type substrate is provided with a buried layer which is doped with large amounts of n-type impurities, an epitaxial layer is grown thereon, and a transistor is formed in the epitaxial layer. With the thus formed transistor, however, as the .alpha.-particles infiltrate from the external side to generate electron and hole pairs in the p-type substrate, the electrons are absorbed by the epitaxial layer through the buried layer and the potential undergoes a change. Therefore, the memory cell using such a transistor leaves a problem with regard to that the data tends to be easily destroyed, and it has been urged to solve this problem.